Materials Combustibility

Many utilities have experienced significant reduction in fault counts by hardening their overhead distribution lines. When undergrounding is not a viable option, the hardening can include stronger poles and crossarms, covered conductors, covered connectors, and specialized coverings and tapes for other exposed and electrified hardware. This is a mature area of application in the grid resilience space. The gap identified by the EPRI wildfire advisory group (and verified with testing at EPRI Lenox) is that when energized equipment fails, the failure mode occasionally ignite portions of the insulating materials, such as synthetic components and coverings like animal guards, tapes, and wraps. EPRI has conducted flame testing on a number of insulative components and the images on this page show the outcomes for a few samples.

The animal guard on the left drips flaming material while the guard on the right flames, chars, and smokes but doesn’t ignite vegetation.

Figure 1: Testing at the EPRI Lab Reveals Many Coverings are not Flame Friendly

EPRI testing on different brands of animal guards, insulating tape, conductor coverings, and other insulating hardware reveal materials and design challenges that warrant new research and development moving forward:

  • First, the materials that the guards, and other insulating electrical coverings are made from doesn’t get consistently specified and designed to be either flame friendly, or moisture ingress proof.
  • Secondly, the same insulative mixtures used for tapes, wraps, and other electric asset coverings have unique combustion concerns whereby the materials can either easily burn or can exacerbate the situation by dripping flaming liquid materials onto the vegetation beneath the coverings.

While these issues don’t apply to every insulating material, testing is advised to better understand how different products and mixtures perform under a flame test. Ideally it would be beneficial to work with one or more of the National Laboratories to develop a selection of improved insulating mixtures that are flame friendly, UV resistant, and weather impervious and provide the criteria to vendors for future products.